Most loading docks have a fixed height which does not always correspond with the bed height of the truck being loaded or unloaded and therefore the concept of an adjustable height ramp unit has been well known in the art for many decades, as typified in the Walker U.S. Pat. No. 3,409,923. This patent discloses a stationary ramp structure which rises out of the floor to the necessary ramp height to fit the specific truck being loaded or unloaded.
Another stationary type of adjustable height ramp structure is taught in the Clark U.S. Pat. No. 3,388,413. In this design the adjustable height ramp is located within the stationary ramp surface. A ramp includes a hinged extension portion transitioning into the truck bed, all of which moves together hydraulically for automatic adjustment to the level of the truck being unloaded.
The Bintliff U.S. Pat. No. 2,670,484, teaches a loading platform structure which is portable in that it moves laterally and provides an adjustable height elevated end while the  opposite end rests on a constant level stationary dock. This platform includes a hinged extension at both ends, as in the present invention. However, it functions differently when elevated and the manner in which it is movable.
The principal object of the present invention is to provide a portable, adjustable height loading ramp which eliminates the need for a stationary dock, thereby permitting a truck to be unloaded at any location where the ramp can be moved to.
Another object of the present invention is to provide an adjustable height wheel-mounted loading ramp which when it is lifted at one end, the transport wheels are all disengaged from the ground whereupon it is supported by plurality of fixed adjustable length telescoping legs, thereby permitting it to support a forklift truck in its now stationary position.
A further object of the present invention is to provide an adjustable height loading ramp with a self-contained power pack which positions the height of the ramp for the particular truck bed being unloaded.